1. Field of the Invention
This invention relates to a photo sensor in which light within a predetermined range is collected by a lens arranged within a package, and the collected light is received by a photo sensing element within the package and converted into an electrical signal.
2. Description of Prior Art
A remote control function to enable a user to perform a desired operation at a remote location is frequently used in electrical equipment such as a television set or a video tape recorder and the like.
In order to perform a remote controlling operation for electrical equipment such as a television set, a photo sensor for sensing an infrared ray beam is arranged at the electrical equipment and a commander for transmitting a signal comprised of an infrared ray beam is prepared for the user.
The user selects an input button or the like set in the commander so as to further select a desired operation and then transmits the infrared ray signal from the commander in response to the desired operation.
At the electrical equipment, the infrared ray signal transmitted from the commander is received at the photo sensor installed in the electrical equipment and converted into a predetermined electrical signal, then the electrical equipment may perform an operation requested by the user in response to this electrical signal.
FIGS. 1A and 1B illustrate the related photo sensor. FIG. 1A is a perspective view and FIG. 1B illustrates a side elevational view in section, respectively.
This photo sensor 1 is comprised of a photo sensing element 10 for receiving an infrared ray beam, for example, and converting it into a predetermined electrical signal; a package 2 made of resin, for example, to make an integral sealing of the photo sensing element 10; electrical lead terminals 3 electrically connected to the photo sensing element 10 within the package 2 and extending downward from the package 2; and a lens 4 arranged at the front surface of the package 2 for collecting the light within the predetermined range toward the photo sensing element 10.
The lens 4 arranged in the package 2 is integrally molded with the package 2, for example, and the lens has a spherical surface in which the distances r.sub.1, r.sub.2 and r.sub.3 measured from the center O of the lens are equal from each other.
With such an arrangement as above, the light within a range of angles of upper angle .alpha. and lower angle .alpha. in respect to a horizontal line, for example, is collected so as to enable the photo sensing element 10 to perform a desired photo-electrical conversion.
Further, since the lens 4 has a spherical surface, it collects light directed not only in the vertical direction but also in the lateral one, then the light collecting range obtained with this lens 4 becomes a sensitivity range attained by a single unit of the photo sensor 1.
FIG. 2 is a schematic diagram for illustrating a state of use of the photo sensor 1.
It is usually found that electrical equipment 11 such as television set or a video tape recorder or the like is installed at a wall side of an indoor area 5.
The photo sensor 1 is set at the front surface of a panel of the electrical equipment 11 to facilitate a receiving of the infrared ray signal.
Under such an arrangement state as above, a user 6 may select a desired operation through the commander 7 at the side of the user and transmit a signal comprising of an infrared ray beam to the photo sensor 1 of the electrical equipment 11.
When the user 6 operates the commander 7 under a condition in which the user 6 stands up, for example, the signal is transmitted from a position slightly higher than the position of the photo sensor 1 (refer to the arrow 1 in FIG. 2).
In addition, when the user 6 operates the commander 7 while the user 6 sits on the floor or something, a signal is transmitted from a position slightly lower than the position of the photo sensor 1 (refer to the arrow 2 in FIG. 2).
A sensitivity range corresponding to the state of use is set at the photo sensor 1 in order to perform a positive receiving of a signal sent from the commander 7.
That is, in the case that a wide sensitivity range is to be attained, a curvature of the lens 4 shown in FIG. 1 is reduced and in turn in the case that a directivity is increased within a narrow sensitivity range, a curvature of the lens 4 is increased.
In addition, in the case that it is desired to reduce the curvature of the lens 4, its sensitivity range is widened, although a rate of collecting light is reduced and a reaching distance of the signal from the commander 7 is made short.
Further, in the case that a curvature of the lens 4 is increased, the sensitivity range is increased, although a rate of collecting light is increased and a reaching distance of the signal from the commander 7 is made long.
In the design of the photo sensor 1, a curvature of the lens 4 corresponding to the state of use is determined in view of this point.
However, such a photo sensor as described above has the following problems.
That is, as shown in FIG. 2, various kinds of lighting devices 8 are normally installed at the indoor area 5 in which the electrical equipment 11 is arranged and some disturbance lights such as infrared ray beams or electro-magnetic wave for use in controlling lighting obtained from the lighting devices 8 are discharged in the room.
As the disturbance lights reach the photo sensor 1 installed in the electrical equipment 11 as shown by the arrow 3 in FIG. 2, they may disturb the photo-electrical conversion performed by the photo sensing element 30 (refer to FIGS. 3A and 3B) and they may become causes to generate erroneous operation.
In the case that a solar light other than the disturbance light projected from the lighting devices 8, for example, enters at a window of a room, this light may similarly cause a similar erroneous operation.
Normally, the disturbance light enters from a position substantially higher than the position of the photo sensor 1, resulting in that it may be assumed that the curvature of the lens 4 is increased so as to improve a directivity and the disturbance light entering from the high position is set out of the sensitivity range. However, the sensitivity range for receiving the requisite signal from the commander 7 is also narrowed and it becomes difficult to get a sufficient remote control function.